satellite even though the transponder was dark. this allows authorities to plot its mysterious course. the search area moves again in late march. >> mh 370 flew at a higher speed than previously thought which in turn means it used more fuel and could not travel as far. australian authorities indicated they shifted the search area 1,100 kilometers to the northeast. >> reporter: high tech listening devices, toad pinger locaters are deployed on the bottom of the sea listening from sound from the pinger attached to the black box. and they peck ick up a signal. the first sign of hope. >> we have very much narrowed down the search area. and we are very confident that the signals that we are dete detecting are from the black box. >> reporter: but the signal fade before the black box is located.